1. Technical Field
The present invention relates to the field of diagnostic testing and, more particularly, to diagnostic testing systems using electronic meters.
2. Background
Diagnostic testing systems are commonly used to perform various types of diagnostic tests on various types of samples. The diagnostic test may be a qualitative or quantitative test to determine the presence, concentration or amount of one or more analytes in a sample. The analyte may be a medically significant analyte—e.g., glucose, ketones, cholesterol, triglycerides, human choriogonadotropin (HCG), hemoglobin A1C, fructosamine, carbohydrates, tumor markers, lead, anti-epilepsy drugs, bilirubin, liver function markers, toxins or their metabolites, controlled substances, blood coagulation factors (PT, ATPP), etc.—contained in a biological sample—e.g., blood, urine, tissue, saliva, etc. However the diagnostic test is not limited to the medical field. In addition, diagnostic test meters can be used to monitor analytes or chemical parameters in non-medical samples such as water, soil, sewage, sand, air, or any other suitable sample.
Such diagnostic testing systems may include a test media (e.g., a test strip, tab, disc, etc.) configured to react to the presence of the analyte in a sample, and a separate electronic meter configured to interface with the test media in order to conduct the diagnostic test and indicate the results of the diagnostic test to the user.
In order to conduct the diagnostic test, a user must first obtain a sample test media, e.g., a test strip, from a container, then obtain a sample using a sampling device (e.g., by drawing blood using a lancet), and then apply the sample to the test media (either before or after inserting the test media into the meter interface). The meter then performs the diagnostic test on the sample and indicates the result to the user, e.g., using a numerical display.
Prior art diagnostic meters are sometimes bulky because the housings contain the display, electronics, and test media. In addition, the user of a blood testing diagnostic system must manage and carry not only the meter, but also a test media container and a sampling device. These three components must be manipulated in a certain order, and require a substantial amount of attention and manipulation to conduct a successful test. Not only are the steps cumbersome to some users, there exists the possibility that the test media container, sampling device and meter could be separated from each other, so that the user may find themselves without one or more of the components necessary to conduct the diagnostic test.
As is known in the art, test media from different manufacturers or media from different manufacturing lots may respond differently to the presence or concentration of analyte in the sample. In order to obtain more accurate results, the electronic meter may be calibrated with respect to a given test strip from a brand or lot of test strips by providing it with one or more brand- or lot-specific calibration parameters that correlate the signal response from a particular brand or lot of test media to a standardized reference. By such calibration, the results reported by the meter more accurately represent the amount of analyte in a sample.
Before running a diagnostic test, the meter needs to be properly calibrated. The user may be required to provide the meter with the appropriate calibration parameters in a separate “coding” step. For example, the test media container may bear a code number which is entered into the meter, and from which the meter can access the appropriate calibration information stored in the meter's memory. The code number can be entered manually (e.g., using buttons or other user input devices on the meter) so as to provide the calibration data to the meter. Alternatively, the calibration data may be downloaded, e.g., from a manufacturer's website. In another approach, the test media container may be provided with an associated code chip, e.g. a ROM, in which the calibration data is stored electronically. The user may provide the calibration data to the meter by inserting the code chip into a corresponding port on the meter.
These prior art coding methods can be inconvenient or difficult for the user. For example, elderly or infirm users may have difficulty downloading calibration data or inserting code chips, which must be physically aligned properly in order to achieve a data connection with the meter. Code chips can be misplaced or lost, leading to the inability to use corresponding test media, or using the test media with an unmatched coding device. Further, users may forget to calibrate the meter for use with a new brand or lot of test media. Consequently, the user may enter incorrect calibration parameters or codes, or the user may use test media from one brand or lot with a meter calibrated for use with test media from a different brand or lot. Once a meter is calibrated for a given lot of test media, the use of that meter with test media from another lot may lead to erroneous results that could have serious consequences for the user. For instance, where the test is a self-test of blood glucose level, an erroneous result could lead the user to act, or fail to act, in a manner detrimental to his or her health.
A possible solution to the above-mentioned coding problems is to insure that all marketed media behave the same. This approach is referred to as “universal coding.” Universal coding schemes use strip lots that are controlled and sorted to a narrow acceptance criteria, i.e. all strips are conformed to a single set of calibration parameters, thus eliminating the needs for multiple sets of parameters to be stored in the meter 130. Universal coding saves the cost of replacing the meter 130 by allowing it to be used with many different test strip containers 110. From a manufacturing perspective, universally coded media 120 needs to be tightly controlled such that manufactured strip lots have the same behavior, and hence code, in order to fit the meter's fixed calibration data. This method is not technique dependent and helps prevent errors due to mixed strip lots. Furthermore, universal coding always has the correct code such that there is no miss-match between the meter 130 and the strip lot code. However, the narrow limits imposed by this method do not conform well to large-scale manufacturing processes, which include inherent variances. It is nearly impossible using high-throughput, batch-oriented manufacturing techniques to ensure that test media will exhibit perfectly consistent behavior, thus the universal coding scheme invariably results in non-conforming lots of media. This media will be unusable, adding to cost and undesirable waste.
Accordingly, there is a need for diagnostic testing systems that are convenient to carry and that minimize the chance that a user will use a diagnostic meter with test media from a brand or lot for which the meter has not been calibrated.